KANSAS CITY, Mo.  Four years ago, Takeo Spikes had seen just about it all.

The linebacker spent a decade in the NFL. He played on three teams in three divisions under five defensive coordinators. He'd been to multiple Pro Bowls, working alongside some of the NFL's best.

He never met someone like Aubrayo Franklin.

The 10th-year nose tackle, in his first season with the Chargers, has been among the key factors to what has proven, so far, to be an improved run defense. Its latest test comes Sunday against the Chiefs' Jamaal Charles, who leads the league in rushing.

Franklin's smarts are arguably his greatest strength.

They stood out immediately to Spikes when signing to become a teammate of his with the 49ers from 2008 to 2010. They were reunited when Franklin, 32, signed a one-year deal in July.

"I'd never been around a D-lineman at the time who studied film like a linebacker and who could tell you tendencies," Spikes said. "From that point on, when I got there, I had to prove my worth all over again.

"It was kind of like we gelled. We started watching film together. He would challenge me: 'What do you see on this?' And I would challenge him: 'What do you see?' It came to a competition where we wanted to find out little idiosyncrasies about another team or personnel, and it fed off to everybody else. Now, what you see out of that (49ers) defense, I feel like that's a product of what we started."

Franklin is a quiet student of the NFL.

He first enrolled in 2003.

The fifth-round draft pick took a crash course with the Ravens. Rex Ryan, now the Jets head coach, was his position coach, and Chargers outside linebacker Jarret Johnson, then a defensive end, was also part of his rookie class.

Ryan taught them not to simply scout the offensive linemen they'd be facing. He made sure they paid attention to the backfield, too, encouraging them to key on different patterns so they could anticipate the playcalling on the field.

"You learn those things and how to play with leverage and tilt and all that stuff, and that's how Aubrayo plays," Johnson said. "He's not just lining up and running straight. He's aggressive, but he's aggressive in certain directions."

Franklin prepares at a high level.

Much of the process comes from studying film and relying on past experiences, but it also includes his usage of the "hit chart."

Each week, the coaching staff will pass out a collection of different formations — when the opponent lines up in 21 personnel, they like to do this; when the running back is positioned here, look there.

"Nine times out of 10, it's dead on," Franklin said. "I mean, you can't just sit there because they can run so many different plays. But you at least know the basics of what you're going to get out of each formation.

"You can label them and put the top three runs out of each formation and study it that way, so then you can get it in your mind, 'OK, well, they're going to block me this way, this way or this way out of this formation.'"

Franklin has started all three games this season for the Chargers.

His presence and rotation at nose tackle with Cam Thomas allowed the Chargers to ease veteran Antonio Garay back into action after he missed several weeks with an ankle injury in training camp.

The team has allowed 67.3 yards per game, fourth in the league.

The combination of more depth and athleticism to go with the development of some of its younger talent has contributed to the Chargers' early strides on the defensive line. The group looks to rebound Sunday after what coaches called its worst game of the season, struggling to generate pressure against the Falcons.

Having Franklin helps.

He seems to always have a tip to share.

Defensive end Vaughn Martin said Franklin knows the game "inside and out" with the keys he has on teams, all the tendencies and percentages. Rookie defensive end Kendall Reyes said he constantly picks Franklin's brain, be it in the film room, locker room or on the field.

"Sometimes, I'm like, 'dang, Bray. How'd you know that?'" Reyes said.

Franklin fits the Chargers better than his previous team.

He left San Francisco as a free agent after the 2010 season and signed with the Saints. It was the first time he played in a 4-3 defensive scheme, and making the jump more difficult, he didn't have OTAs or a minicamp to ease the transition because of the lockout.

His production suffered.

In San Diego, he's the same guy Spikes remembered.

"My game was totally different than the type of style they wanted me to play," Franklin said. "I feel like I did it good, but I'm a better 3-4 nose tackle than I am a 4-3 (tackle), not to try to limit myself. I know my body limitations, and I know what I'm good at.